Field of the Invention
This application is related to a rotary seal assembly permitting a passage of high pressure fluid in the field of oil and gas drilling operations, particularly, to a washpipe assembly used in oil and gas drilling equipment, such as a drilling rig swivel, or a top drive.
Description of the Related Art
A washpipe device, which is utilized to provide a rotary passage between a gooseneck and a main shaft in order to deliver high pressure drilling fluid from mud pumps to a drilling bit, is one of the most important members of a drilling rig swivel or a top drives in oil and gas drilling operations. In particular, a washpipe assembly, which is easy to install and maintain, and which is operational with high pressure and of a long working life, contributes safety and efficiency of oil and gas operations.
There are two types of washpipe assembly, the traditional washpipe assembly which utilizes a stack of elastomeric rotary seals against the external cylindrical sealing surface of a metal pipe to provide a dynamic sealing arrangement, and the mechanical seal washpipe device which utilizes a floating seal member together with rotating seal ring and stationary seal ring to provide a dynamic sealing arrangement. The traditional type have a limited lifetime of approximately 200 hours or less in average, and have difficulty to replace the sealing arrangement because the device is installed at a high location, in a limited space, and configured with heavy hammer unions.
U.S. Pat. No. 7,343,968 B2 issued on Mar. 18, 2008 to Zbigniew Kubala provides a mechanical seal type sealing arrangement which utilizes a floating seal assembly having a stationary seal ring mounted to first drilling fluid conduit member or gooseneck and which is structurally arranged to engage a rotating seal ring which is mounted to a second conduit member or the rotating main shaft. The tubular washpipe member is structurally fixed to the stationary structure, and the floating seal assembly is aligned to the stationary structure with anti-rotating pins.
During the operation, as the rotating main shaft brings the rotating seal ring to rotate while the stationary seal ring is pressed to the rotating seal ring without rotation, the friction between the two rings is delivered from the stationary seal ring to the stationary structure through the floating seal member and the anti-rotating pins, and in the meantime, the rotating main shaft produces shaft runout and axis jump. The force between the floating seal member and the anti-rotating rods damages the floating function of the floating seal assembly. The fixed installation of the washpipe member with respect to the stationary structure and the limited cylindrical clearance between the floating seal member and the washpipe member also limits the following capacity of the stationary seal ring to the rotating seal ring. The limited floating and/or following capacity of the above mentioned washpipe assembly asks a demanding installation interface, which results in a difficult installation and commissioning work.
In prior arts, the O-ring groove for installing the O-ring between the upper seal ring and the floating seal member is configured in the floating seal member, and the O-ring groove for installing the O-ring between the lower seal ring and the lower nut is configured in the lower nut. Because the O-ring grooves are directly exposed to the drilling fluid during the operations, and the space for replacing the seal rings is very limited, it takes time to clean the grooves when replacing seal rings, which results in an extended downtime of the drilling operations.